1. Field of the Invention
The present invention relates to a combined, continuously operating high-speed light-section mill and wire mill with a roughing train, at least one intermediate train and a subsequent finishing train, wherein each of the trains includes several rolling mill stands or rolling units, and possibly a subsequent finishing stand set.
2. Description of the Related Art
In accordance with German patent application P 39 40 236.5 which is not yet published, in a rolling mill train of the above-described type, it is proposed that the roll exchange takes place in accordance with the minimized series of passes in each train section. The exchange is carried out in the roughing train by means of crane tools, in the intermediate train by means of manipulators and in the finishing train by means of a quick-exchange device and possibly additional manipulators, wherein all rolling mill stands or rolling units in the individual train sections have overhung-mounted rolls which can be pulled out, in order to increase the availability and the yield of the rolling mill train.
Rolling mill stands with overhung-mounted collars are designated in the art as cantilever stands or abbreviated as CL stands. Thus, a particular feature of these modern compact stand constructions are the overhung-mounted or cantilevered roll shafts. Collars of highly wear-resistant materials ensure long pass service lives.
The vertical roll stands are driven from below. An intermediate gear unit is arranged between motor and stand. In vertical stands, the intermediate gear unit is a bevel gear unit and in horizontal stands the intermediate gear unit is a spur gear unit. In the stand itself, the drive shaft simultaneously drives the auxiliary shaft and one of the two roll shafts. The other roll shaft is driven through the auxiliary shaft. The drive shaft and the auxiliary shaft, as well as the roll shafts, are tempered to high strengths and ground. The roll shafts run in friction bearings which are mounted in rotatable eccentric bushings.
The collars are adjusted simultaneously. The adjustment is effected by rotating the eccentric bushing through an adjusting spindle having a thread with an oppositely directed pitch direction. The pass line remains constant. The axial forces occurring during rolling are absorbed by an inclined ball bearing which is mounted without axial play. As a result of this feature, and because the roll shafts are positioned exactly parallel to each other and rolling is carried out without twisting and without tension, a rolled product of high quality is obtained. The stand exchange times, i.e. the exchange times for the collars as well as the exchange times for the entire gear boxes including the collar, are so short that the stands are practically continuously ready for operation. Specially constructed looping stands are not necessary.
In a rolling mill train consisting of CL stands, the rolling pressure exerted by the material being rolled always is conducted into the first bearings of the overhung-mounted rolls. As a result, when rolling high initial pass cross-sections and with high deformation resistances, the collars, the bearings and the housings must have appropriately large dimensions. These large dimensions of the individual components of the stands result in the danger that the compact construction of the CL stands is essentially lost. Accordingly, large initial pass cross-sections and high rolling forces lead in the typical CL stands to technological and structural limits. This technical problem could be overcome by using conventional stands without posts and with rolls which are mounted on both sides in chocks, for example, stands with housing posts and with rolls with one or more passes which are mounted on both sides in the post windows in the chocks. However, these stands are expensive, require a large amount of space and intensive maintenance when the rolls are to be changed for other passes.
As a rule, the intermediate train and the finishing train of a wire mill and light-section mill equipped with CL stands is not capable of rolling sections because this can generally lead to dimensional inaccuracies due to the fact that the rolls are mounted in an overhung manner. If this were to be done nevertheless in the past, separate conventional rolling stands with the rolls being mounted on both sides would have to be introduced in the pitch line. This is an expensive and cumbersome solution because the rolling mill train is predominantly to be used for wire and round steel dimensions.